conventional liquid ring vacuum pumps comprise multiple impellers and an adjustable spacer bushing disposed between the impellers. The removable impellers and spacer are secured about the shaft by means of a locknut which is disposed at one end of the shaft and a shaft shoulder which is disposed at the opposite end of the shaft.
One conventional method for assembling a liquid ring vacuum pump as shown in FIG. 1, comprises the attaching of a first stage endcasing 1 to a bearing housing 11 which includes a ball bearing 17. Endcasing 1 and bearing housing 11 are thereafter mounted on an assembly stand 100 for vertical assembly of pump 110. Side plate 3 is then attached to endcasing 1 (screws are not shown). Center shaft 12 having a shaft shoulder 120 disposed at one end thereof is inserted vertically into bearing 17. After inserting key 19 into shaft 12, a first stage impeller 7 is fitted about shaft 12 such that shaft shoulder 120 is disposed between impeller 7 and side plate 3. It should be noted that key 19 and impeller 7 can alternatively be mounted about shaft 12 prior to insertion of shaft 12 into bearing 17. Thereafter, first stage impeller housing 9 is affixed to side plate 3, while suction plate 5 and discharge plate 4 are joined to form a center housing. Plates 4 and 5 are then affixed to first stage impeller housing 9. Alternatively, plates 4 and 5 can be formed as a one piece center housing which is also affixed to impeller housing 9. An impeller spacer bushing 30 is disposed on shaft with clearance to the inside diameters of suction plate 5 and discharge plate 4.
After installing key 20 on shaft 12, a second stage impeller 8 is mounted about shaft 12. Second stage impeller housing 10 is connected to plates 4 and 5 such that it encases second stage impeller 8. Thereafter, an impeller locknut 31 is placed about shaft 12 and tightened via threads disposed on the surface of shaft 12. The tightening of locknut 31 secures impellers 7 and 8 and spacer 30 as a single unit against shaft shoulder 120. Separately, side plate 6 is fastened to second stage endcasing 2 which is then fastened to non-drive end bearing housing 122 with radial alignment of feet disposed at the bottom of endcasing 2 and top flanges connected to conduit 28.
A set of continuous tie 23, only one shown by ways of example, are installed between endcasings 1 and 2 and torqued to join the entire pump assembly. Conversely, when tie rods 23 are loosened in order to repair or perform periodic maintenance on pump 110 the entire pump 110 is disassembled. That is, endcasings 1 and 2, impellers 7 and 8, and spacer bushing 30 will separate from each other upon the loosening of tie rods 23 such that they must be resealed and adjusted before reassembling pump 110 and re-tightening of tie rods 23.
Assembly of such a conventional pump as shown in FIG. 1 (i.e., in the vertical mode) requires stacking of all of the static housing components with intermediate gaskets or sealant, and the rotating shaft/impeller parts before securing the entire assembly together by means of various tie rods disposed between the endcasings of both the drive and the non-drive ends of the shaft. Impeller end clearances are difficult to equalize and control during this systematic layer-upon-layer assembly method. Moreover, during disassembly or repair the entire pump must be broken down and all sealing joints have to be redone prior to reassembling of the pump.
The present invention provides a unique pump assembly which overcomes the assembly/disassembly problems associated with conventional pumps by permitting the independent assembly and disassembly of each impeller stage about the shaft. This is accomplished by mounting each impeller on the shaft on opposite sides of a novel fixed center shaft shoulder and thereafter securing each impeller in place by means of its associated locknut. A plurality of tie rods (i.e., securing means) are independently secured between the center housing and each respective first and second stage endcasings. This allows for the independent assembly or disassembly of each static housing side (i.e., either the static first stage housing side or static second stage housing side), whereby each impeller can be independently repaired or replaced without requiring the disassembling of the other impeller unit. The independent assembly of either impeller unit results in a substantial savings in terms of both repair time and material costs versus conventional pumps which require the replacement of gaskets and sealings and re-alignment of the non-repaired impeller unit whenever the pump is disassembled.
The present invention provides for an easier assembly/disassembly of liquid ring vacuum pumps, as well as enables proper control of critical end clearances between the impeller and their associated endcasing.
The present invention also provides many additional advantages which shall become apparent as described below.